The overall objective of the proposed research is to study the structure and function of some sugar-binding proteins mainly by X-ray crystallographic technique. These proteins are essential components of some specific transport systems in bacterial cells. Two sugar-binding proteins will be studied, namely, L-arabinose- and D-galactose-binding proteins. These proteins participate in the cellular accumulation of L-arabinose and D-galactose, respectively. The crystal structure of L-arabinose-binding protein at 3.5 A resolution has been determined. This research will contribute to some understanding of the role of these proteins in transport systems and their mode of folding and stability of their unique three-dimensional structure. In view of the presently held concept that binding proteins are involved in transport processes and would therefore be expected to function and interact in a membrane environment, this study will provide some understanding also of the nature of protein-membrane interaction. BIBLIOGRAPHIC REFERENCES: Quiocho, F.A., with Phillips, G.N., Emery, H., Knapp, F.F., and Schroepfer, G.J., Jr., Sterol Synthesis. Structure of 3-p-Bromobenzoxy-loxy-Cholest-8(14)-ene-15-ol, Book of Congress, 10th International Congress of Crystallography, No. 06.1-40 (1975). Quiocho, F.A., with Phillips, G.N., Jr., Mahajan, V.K., and Siu, A.K.Q., Crystallographic Analysis of an L-Arabinose-Binding Protein from E. coli, Book of Congress, 10th International Congress of Crystallography, No. 03.1-11, (1975).